Effect of crosslink density on fracture behavior of model epoxies containing block copolymer nanoparticles

• Published in: Polymer (Guilford) Vol. 50; no. 19; pp. 4683 - 4689
• Main Authors: Liu, Jia (Daniel), Sue, Hung-Jue, Thompson, Zachary J., Bates, Frank S., Dettloff, Marv, Jacob, George, Verghese, Nikhil, Pham, Ha
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 10.09.2009; Elsevier
• Subjects: Applied sciences; Block copolymer nanoparticle; Crosslink density; Epoxy toughening; Exact sciences and technology; Mechanical properties; Organic polymers; Physicochemistry of polymers; Properties and characterization; Block copolymer nanoparticle; Epoxy toughening; Crosslink density; Strengthening; Molecular structure; Mechanical properties; Epoxy resin; Isoprene derivative copolymer; Ethylene oxide copolymer; Experimental study; Mechanism; Fracture toughness; Saturated copolymer; Dynamic mechanical properties; Diblock copolymer; Property structure relationship; Modified material
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2009.05.006

Model diglycidyl ether of bisphenol-A based epoxy resins containing well-dispersed 15nm block copolymer (BCP) nanoparticles were prepared to study the effect of matrix crosslink density on their fracture behavior. The crosslink density of the model epoxies was varied via the controlled epoxy thermoset technology and estimated experimentally. As expected, it was found that the fracture toughness of the BCP-toughened epoxy is strongly influenced by the crosslink density of the epoxy matrix, with higher toughenability for lower crosslink density epoxies. Key operative toughening mechanisms of the above model BCP-toughened epoxies were found to be nanoparticle cavitation-induced matrix shear banding for the low crosslink density epoxies. The toughening effect from BCP nanoparticles was also compared with core-shell rubber-toughened epoxies having different levels of crosslink density. The usefulness of the present findings for designing toughened thermosetting materials with desirable properties is discussed. [Display omitted]